Tenatoprazole, or (+)-5-methoxy-2-{[(4-methoxy-3,5-dimethyl-2-pyridyl) methyl] sulfinyl} imidazo-[4,5-b] pyridine, is described in Patent No. EP 254,588. It belongs to the group of drugs considered as proton pump inhibitors, which inhibit the secretion of gastric acid and are useful in the treatment of gastric and duodenal ulcers. It can also be used to treat gastro-oesophageal reflux, digestive bleeding and dyspepsia, because of its relatively long elimination half-life, as described in the application for French patent No. FR 02. 13113.
The first known derivative of this series of proton pump inhibitors was omeprazole, described in Patent No. EP 001,529, which is endowed with properties which inhibit the secretion of gastric acid and is widely employed as an anti-ulcerative in human therapeutics.
In addition to omeprazole, other proton pump inhibitors are well known, and particular mention can be made of rabeprazole, pantoprazole and lansoprazole, which all exhibit structural analogy and lansoprazole, which all exhibit structural analogy and belong to the group of pyridinyl methyl sulfinyl benzimidazoles. These compounds are sulfoxides presenting with asymmetry at the level of the sulphur atom, and therefore generally take the form of a racemic mixture of two enantiomers.
Like omeprazole and other sulfoxide with an analogue structure, tenatoprazole has an asymmetric structure and may therefore be present in the form of a racemic mixture or of its enantiomers. Thus it may exist in the form of its two enantiomers with R and S configurations, or (+) or (−), respectively.
Recent studies have shown that, unlike all the other proton pump inhibitors such as, for example, omeprazole or lansoprazole, and unexpectedly, tenatoprazole is endowed with a markedly prolonged duration of action, resulting from a plasma half-life which is about seven times longer. Thus the clinical data collected have shown that tenatoprazole enables a degree of symptom relief and healing of gastric lesions which is superior to that achieved by other drugs belonging to the same therapeutic category of proton pump inhibitors, which thus allows its effective use in the treatment of atypical and oesophageal symptoms of gastro-oesophageal reflux, digestive bleeding and dyspepsia, as indicated above.
Studies performed by the application have made it possible to show that the two enantiomers contribute differently to the properties of tenatoprazole, and that the two enantiomers, (+) and (−) exhibit significantly different pharmacokinetic properties. Thus it is possible to prepare medicinal products with specific activity by isolating the enantiomers, and these enantiomers themselves exhibit a different pharmacokinetic profile from that of the known racemic mixture. It then becomes possible to use each of these enantiomers more effectively in precise indications for the treatment of perfectly identified pathologies.